For adding text, you have a few options. The plugin has a built-in feature which will take the “Default Merge Tag Value” set inside of your MailChimp list, and make that the default value pre-filled in your sign up form field’s input area. This article walks through how to set Default Merge Tag Values up:
How do I set default merge values (like Dear Customer)?: http://eepurl.com/hcDC
Once those are set up, make sure to go in your plugin’s settings in the WordPress admin area and refresh/update your list info.
Alternatively, if you prefer “placeholder” text, you can use the workaround/alteration to the code, suggested by a fellow WordPress user here:
http://ww.wp.xz.cn/support/topic/plugin-mailchimp-list-subscribe-form-request-add-placeholder-text-for-mailchimp-widget?replies=21
In regards to making the field labels hidden, you can do that by setting some CSS code like so:
#mc_signup_form .mc_var_label {
display: none;
}
If you have any questions, let us know!